A positioning system for an original passed one or more times through a copying path of a copying apparatus is disclosed in U.S. Pat. No. 4,058,359. In that system, use is made of photodetectors on both sides of a desired line of transport of a side edge of an original. If a detector at the inner side of the transport line is not illuminated while a detector at the outer side of the line is illuminated, then the side edge of the original is deemed to be located within a tolerance range relative to the desired transport line. During a repeated transport of the original through the copying path for the production of several copies from the same original, however, it can happen that the original gradually deviates from the desired transport line, displacing slowly to the left or right of the line. As a result, instances can arise in which the side edge of the original is displaced so far in one direction that the original is moved beyond the range of the inner detector that originally was not illuminated. It also can occur in some circumstances that the original becomes displaced so far in the other direction that both detectors are covered by the original and thus neither detector is illuminated.
In both types of displacement of the original a position correction means is operated in such a way that the side edge of the original is brought back within the tolerance range relative to the desired transport line.
A suitable position correction means, as shown in U.S. Pat. No. 4,058,359, includes a roller over which the original is transported and which is journalled at both ends in such a way that the roller can be displaced axially. A lever is employed which engages in a recess of the roller, and by which the roller can be moved over a predetermined distance in the axial direction, either to the left or to the right. Friction elements on the roller increase the grip exerted by the roller on the original. During the transport of the original over the roller, and preferably immediately after the leading edge of the original has passed the roller, the roller can be moved by the lever to the left or to the right. This motion causes the original to be displaced a predetermined distance either to the left or to the right to correct a deviation of the original from the desired transport line.
As described in the cited patent, the original is fed in along a lateral guide beyond which the side edge of the original is to be detected. The detectors in the position detector are so positioned that when the original has been fed in with a side edge at the lateral guide, the side edge then passes between the detectors and is deemed to be within the tolerance range of the ideal transport route. It will be obvious that if in the embodiment of the U.S. Pat. No. 4,058,359 the lateral guide is displaced laterally, the detectors must be correspondingly displaced. Such displacement of the lateral guide may be desired, for example, when an edge of the original is provided with a suspension strip or other marginal strip that is not to be copied. In such a case, the lateral guide needs to be displaceable so that the suspension strip or marginal strip will lie just outside the surface to be copied; but when that is the case the detectors need to be mechanically linked to the lateral guide, thus introducing problems.